3192 - The Influence of Implanting Prostheses of Different Materials after Radical Mastectomy for Breast Cancer on the Accuracy of Radiotherapy

Purpose/Objective(s): There are various types of prostheses that can be implanted after radical mastectomy for breast cancer. During radiotherapy, these prostheses may undergo shape changes, which can affect the accuracy of treatment. This study compares the changes of two types of prostheses during radiotherapy, analyzes the correlation between the changes of prosthesis-related measurement indicators and treatment displacement, and provides evidence-based support for optimizing clinical treatment plans

Materials/Methods: One hundred breast cancer patients who received radiotherapy in our department were selected and divided into three groups according to the different materials implanted after surgery: Group A (silicone prosthesis implantation group) with 28 cases, Group B (water-filled prosthesis implantation group) with 25 cases, and Group C (breast-conserving treatment control group) with 47 cases. All patients were fixed in the supine position with foam rubber. During CT positioning, the plane with the maximum protrusion of the prosthesis or the plane of the nipple was taken, and a solid line was drawn from the midline of the body to the posterior axillary line on the affected side. The distance of this solid line was measured with a soft ruler and recorded. During radiotherapy, cone-beam CT (CBCT) verification was performed before the 1st, 6th, 11th, 16th, and 21st treatments, and the displacement data in the X-axis (left-right direction), Y-axis (head-foot direction), and Z-axis (abdominal-back direction) were recorded. At the same time, the distance of the solid line on the body surface was measured, and the difference between the positioning measurement value and the measurement value at each treatment time point was calculated (referred to as the change value of the solid line distance)

Results: The distances of the solid lines on the body surface of groups A, B, and C gradually decreased, and the change values of the solid line distances increased gradually with the increase in the number of treatments. Among them, the reduction amplitudes and change values of the solid line distances in group A and group B were significantly greater than those in group C (P < 0.05). Correlation analysis showed that the change values of the solid line distances in group A and group B were significantly correlated with the X-axis and Z-axis displacement data verified by CBCT (P < 0.05), while there was no statistical significance for the Y-axis displacement

Conclusion:

For patients who have undergone radical mastectomy and have silicone or water-filled prosthesis implanted, the body surface marking distances will change during radiotherapy, and the change range will increase as the number of treatments increases. When performing radiotherapy on patients with prosthesis implantation, the frequency of CBCT verification should be increased in the middle and later stages, and CT positioning should be re-conducted if necessary to improve the accuracy of radiotherapy.